![SelectQuery with qualifier
ObjectContext context = ...
SelectQuery<Artist> query = new SelectQuery<Artist>(Artist.class);
query.andQualifier(Artist.NAME.like("A%"));
query.andQualifier(Artist.DATE_OF_BIRTH.lt(new Date()));
List<Artist> someArtists = context.select(query);
INFO: SELECT t0.NAME, t0.DATE_OF_BIRTH, t0.ID FROM ARTIST t0 WHERE (t0.NAME LIKE ?) AND (t0.DATE_OF_BIRTH < ?)
[bind: 1->NAME:'A%', 2->DATE_OF_BIRTH:'2013-05-09 20:51:12.759']
INFO: === returned 1 row. - took 2 ms.](https://image.slidesharecdn.com/2apachecayenneforwebobjectsdevelopers-130623091446-phpapp01/85/Apache-Cayenne-for-WO-Devs-40-320.jpg)
Apache Cayenne for WO Devs
- 1. Apache Cayenne for WO Devs by Andrus Adamchik, ObjectStyle LLC
- 2. • 2001 - inception • 2002 - first “alpha” release and a large production deployment • 2006 - Cayenne becomes “Apache Cayenne” • still active and evolving... History
- 3. • A top-level project at Apache Software Foundation • 17 committers • 9 PMC members • Majority of PMC have WO/EOF background • ... not all are active ... Project Structure and Governance
- 4. Releases • 3.0 - current stable • 3.1 - Beta, recommended for all users • 3.2 - in development; used for this presentation
- 6. Separate DB and Object Layers
- 7. DB layer: DbEntities containing DbAttributes and connected with DbRlationships • DbEntity - models a table or a view • DbAttribute - models a column • DbRelationship - models PK/FK relationship going in one direction
- 8. Object layer: ObjEntities containing ObjAttributes and connected with ObjRlationships • ObjEntity - models a persistent Java class • ObjAttribute - models a “simple” property of a Java class • ObjRelationship - models a “relationship” property, i.e. a property of type that is another ObjEntity (can be to-one or to- many). Going in one direction only.
- 9. Connecting Obj to Db Layer • ObjEntity references a single DbEntity
- 10. Connecting Obj to Db Layer • (simple attribute) ObjAttribute references a DbAttribute • (flattened attribute) ObjAttribute references a “dbpath” across one or more DbRelationships ending with an attribute
- 11. Connecting Obj to Db Layer • (simple relationship) ObjRelationship references a DbRelationship • (flattened relationship) ObjRelationship references a “dbpath” across 2 or more DbRelationships
- 12. CayenneModeler
- 13. Cross-platform natively-packaged tool to work on Cayenne mapping projects
- 14. Tools > Reengineer Database Schema
- 15. Tools > Generate Database Schema
- 16. Tools > Migrate Schema
- 17. Tools > Generate Classes
- 18. Tools > Import EOModel
- 19. Modeling Workflow
- 20. Challenge - keeping these in sync:
- 21. Maven and Ant Tools • cgen - generates classes from the ORM model • cdbimport - generates model from DB • cdbgen - generates DB from the model
- 22. Modeler Workflow ... on project start:
- 23. Modeler Workflow ... on each iteration:
- 24. Modeler-Free Workflow ... on project start:
- 25. Modeler-Free Workflow ... on each iteration:
- 26. Modeler-free Workflow - Maven <plugin> <groupId>org.apache.cayenne.plugins</groupId> <artifactId>maven-cayenne-plugin</artifactId> <configuration> <map>${project.basedir}/src/main/resources/my.map.xml</map> <destDir>${project.basedir}/src/main/java</destDir> <defaultPackage>com.example.cayenne</defaultPackage> <superPkg>com.example.cayenne.auto</superPkg> <url>jdbc:mysql://127.0.0.1/mydb</url> <username>user</username> <password>secret</password> <driver>com.mysql.jdbc.Driver</driver> <excludeTables>migrations</excludeTables> </configuration> <executions> <execution> <id>default-cli</id> <goals> <goal>cdbimport</goal> <goal>cgen</goal> </goals> </execution> </executions> </plugin>
- 27. When to use Modeler-free workflow? • when DB objects have sane naming • when DB has FK constraints defined • when no per-entity model tweaking is needed (optimistic locking, PK generation, exclusion of attributes, etc.)
- 28. Writing Apps with Cayenne
- 29. Starting Cayenne // create reusable ‘runtime’ instance ServerRuntime runtime = new ServerRuntime("cayenne-myproject.xml");
- 31. ObjectContext
- 32. Obtaining ObjectContext // regular context ObjectContext context = runtime.newContext(); // nested context ObjectContext nestedContext = runtime.newContext(context);
- 33. ObjectContext • An isolated “session” to access Cayenne • Has its own copy of each object • Doesn’t require explicit shutdown (can be simply thrown away when no longer in use) • Can be serialized • Can be scoped differently based on app requirements
- 34. Under the Hood ServerRuntime is a DI container
- 35. Overriding a DI service to create custom ObjectContexts public class MyContextFactory implements ObjectContextFactory { @Inject private EventManager eventManager; @Override public ObjectContext createContext() { return new MyContext(eventManager); } @Override public ObjectContext createContext(DataChannel parent) { return new MyContext(parent, eventManager); } } Module myModule = new Module() { @Override public void configure(Binder binder) { binder.bind(ObjectContextFactory.class).to(MyContextFactory.class); } }; // override built-in services via a custom module ServerRuntime runtime = new ServerRuntime("cayenne-myproject.xml", myModule);
- 36. DI Container Highlights • Very small - 40K • Intended to make Cayenne runtime modular and customizable • Does not interfere with or care about application DI • Can be used outside Cayenne, but this was not the goal
- 37. Queries
- 38. SelectQuery • Most commonly used query • Data rows option • Fetch offset/limit • Prefetching (separate strategies) • Result caching, pagination • Iterated result
- 39. SelectQuery ObjectContext context = ... SelectQuery<Artist> query = new SelectQuery<Artist>(Artist.class); List<Artist> allArtists = context.select(query);
- 40. SelectQuery with qualifier ObjectContext context = ... SelectQuery<Artist> query = new SelectQuery<Artist>(Artist.class); query.andQualifier(Artist.NAME.like("A%")); query.andQualifier(Artist.DATE_OF_BIRTH.lt(new Date())); List<Artist> someArtists = context.select(query); INFO: SELECT t0.NAME, t0.DATE_OF_BIRTH, t0.ID FROM ARTIST t0 WHERE (t0.NAME LIKE ?) AND (t0.DATE_OF_BIRTH < ?) [bind: 1->NAME:'A%', 2->DATE_OF_BIRTH:'2013-05-09 20:51:12.759'] INFO: === returned 1 row. - took 2 ms.
- 41. Other Queries • EJBQLQuery • SQLTemplate • ProcedureQuery • ObjectIdQuery, RelationshipQuery, QueryChain • Custom queries...
- 43. Can be used with any Query and is fairly transparent SelectQuery<Artist> query = new SelectQuery<Artist>(Artist.class); query.andQualifier(Artist.ARTIST_NAME.like("A%")); // This is all it takes to cache the result. // There’s no need to calculate a cache key. // Cayenne will do that for you query.useLocalCache(); List<Artist> someArtists = context.select(query);
- 44. Lifecycle Events • PostAdd, PrePersist, PreUpdate, PreRemove, PostPersist, PostUpdate, PostRemove, PostLoad • Persistent objects can declare callback methods to be notified about own events • Any non-persistent object can be a listener for various entity events.
- 45. Lifecycle Events • Higher-level “workflows” are implemented by matching entities with listeners using custom annotations and providing operation context via DataChannelFilter
- 47. ROP Highlights • Same as nested ObjectContext, only child context lives in a remote JVM • Full ORM API and behavior available on the client: • Queries, lazy relationships, caching, pagination, etc. • Client objects based on the same model as server • Client objects are using a different superclass
- 48. Other ORM Choices • Hibernate • JPA
- 49. Cayenne Difference - Object Design Others enhanced/proxied POJO ORM Annotations Cayenne framework superclass annotations used for other things Advantage faster startup times “WYSIWYG” objects generic persistent objects less code clutter
- 50. Cayenne Difference - Runtime Others explicit transactions Cayenne on-demand implicit transactions Advantage less code, cleaner code seamless relationship navigation
- 51. EOF Analogies “All characters and events – even those based on real people – are entirely fictional.”
- 52. Persistent Objects • EOEnterpriseObject : Persistent, DataObject, CayenneDataObject • EOGlobalID : ObjectId • EOGenericRecord : CayenneDataObject
- 53. Mapping • EOModel : DataMap • EOModelGroup : EntityResolver • EOEntity: DbEntity / ObjEntity
- 54. Query • EOFetchSpecification : SelectQuery • EOQualifier : Expression • EOSortOrdering : Ordering
- 55. Runtime • EOEditingContext : ObjectContext • EOAdapter : DataNode • JDBCPlugin : DbAdapter
- 56. Cayenne != EOF
- 57. WhatYou Might Miss from EOF • QuirkyVertical Inheritance • No Horizontal Inheritance • No prototypes • No Eclipse plugin
- 58. WhatYou Get in Return • Multithreading • IDE-independent Modeler • Internal dependency injection • Query abstraction beyond SelectQuery • EJBQL and aggregated queries • Iterated query • Transparent Query result cache • Transparent Query result pagination • Auto-increment PK • Automated DB type detection • Prefetch strategies • Lifecycle events
- 59. A chance to influence things!